This commit cleans up the tracer implementation by removing the unused Submit and SubmitChunk methods.
Additionally, it updates the Chunk type to chunk in various places throughout the codebase.

Signed-off-by: Kemal Akkoyun [email protected]

What does this PR do?

This PR refactors the tracer implementation by:

• Removing unused Submit and SubmitChunk methods from the public API
• Unexposing the Chunk type by renaming it to chunk (making it private)
• Updating all related code to use the new private type
• Cleaning up the public API surface to be more maintainable

This is a follow-up to:

• chore(ddtrace/tracer): remove unused exported functions #3563: chore(ddtrace/tracer): remove unused exported functions
• refactor(ddtrace/{tracer,mocktracer}): remove SubmitChunk method fromTracer interface #3562: refactor(ddtrace/{tracer,mocktracer}): remove SubmitChunk method from Tracer interface
• refactor(ddtrace/tracer): remove Submit method from Tracer interface #3561: refactor(ddtrace/tracer): remove unused Submit method from Tracer interface

Motivation

The changes improve code maintainability by:

• Reducing the public API surface by removing unused methods
• Making internal implementation details private where appropriate
• Simplifying the codebase by removing unnecessary public interfaces
• Following Go best practices of keeping implementation details private
• Continuing the cleanup work started in the referenced PRs

Reviewer's Checklist

• Changed code has unit tests for its functionality at or near 100% coverage.
• System-Tests covering this feature have been added and enabled with the va.b.c-dev version tag.
• There is a benchmark for any new code, or changes to existing code.
• If this interacts with the agent in a new way, a system test has been added.
• New code is free of linting errors. You can check this by running golangci-lint run locally.
• Add an appropriate team label so this PR gets put in the right place for the release notes.
• Non-trivial go.mod changes, e.g. adding new modules, are reviewed by @DataDog/dd-trace-go-guild.